Nano-Composite and Method of Producing the Same

ABSTRACT

The present invention is related to a method of producing nano-composites, which has the following steps: providing a solution, the solution has a substrate and a precursor of a zero-dimensional nanoparticles; subjecting a surface of the solution to a plasma to activate the precursor to generate the zero-dimensional nanoparticles in the solution; whereby the nanoparticles are self-assembled on the substrate uniformly to generate the nano-composites.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a method for producing anano-composite, and particularly a method for manufacturingself-assembling nano-composite by plasma.

2. Description of the Prior Art

Nanoparticles, such as the precious metal gold (Au), silver (Ag),platinum (Pt) nanoparticles, have been widely used and generally inchemical reaction as catalyst. Germanium (Ge) applied with nanotechnology is greatly used in the semiconductor industry. Iron (Fe),cobalt (Co), nickel (Ni) and other transition metal nanoparticles wereoverwhelmingly applied to military, civilian or electronic industry,etc. Due to high specific surface area or enhanced mechanical, modifiedphysical and chemical properties of the metal nanoparticles, thedevelopment of nanometer-grade metal materials continuously acquirespublic attention.

Conventional preparation of nanoparticles is mainly performed by a wetchemical method. This kind of method has an advantage on the productionyield. However, for the present preparation method, the reaction timerequired for preparation is too long (typically several hours arerequired), the size of nanoparticles is not even, excessiveagglomeration of nanoparticles occurs or the additional purificationsteps to obtain the nanoparticles are too cumbersome, and the usedsurfactant or chemicals results in environmental pollution. Accordingly,the above problems are significantly limiting the development ofnanoparticles.

In order to render nanometer-grade materials multiple-functional, manyresearches have attempted to take advantage of the semiconductormanufacturing process to generate nano-composite structure. However, themanufacturing process yields little nano-composites and is completelynot feasible or beneficial to vast production, which results in a greathindrance in its industrial application.

SUMMARY OF THE INVENTION

In order to change the above-mentioned shortcomings of manufacture ofnanoparticles and to solve the problems of methods for producingnano-composites yielding less and lacking of industrial use, the presentinvention provides a method of producing nanoparticles with uniformparticle size by utilizing plasma process, which allows thenanoparticles directly being adsorbed on a pre-selected substrate, sothat nanoparticles can self-assemble on the pre-selected substrate.Since the substrate is selected nanometer grade, a resultant differentdimensional nano-composite is thus quickly and conveniently generated.

The present invention provides a method for producing nano-composite,comprising the steps of:

providing a reaction solution containing at least one dimensionalnanomaterials and a precursor of zero-dimensional nanoparticles; and

applying plasma to a surface of the reaction solution or in the reactionsolution to generate the zero-dimensional nanoparticles from theprecursor of the zero-dimensional nanoparticles to assemble on the atleast one dimensional nanomaterials to obtain a nano-composite dispersedin the reaction solution.

The present invention also provides a diverse multiple-dimensionalnano-composite, which is formed by binding the zero-dimensionalnanoparticles to the surface of the at least one dimensionalnanomaterials, which is due to the electrical potential difference,different charge, surface characteristics or attraction betweenmolecules.

In this way, the present invention includes the following features toachieve the following technical effects:

1. the present invention provides a method for directly producing alarge amount of nanoparticles with evenly dispersion through theadjustment of formulation to generate nanoparticles directly synthesizedor attached on a surface of a selected substrate, nanoparticles beinguniformly attached to the surface of the substrate, which results in anadvanced method of producing a self-assembled nano-composite havingdiverse multiple-dimensional structure to solve the problem inindustrial production of nanoparticles, and more to solve the problem inredundant procedure for dispersion of nanoparticles or nano-composites;

2. the present invention provides a solution for resolving the need ofnanomaterials for different purpose, by choosing desired nanoparticlesand substrates to obtain various diverse multiple-dimensionalnano-composite, which result from precise choice of material to grow toconcur the barrier of current technique to provide a more diverse, lessrestrictive, more simple and efficient method for producing the same;

3. the present invention utilizes plasma manufacturing process toincrease absorption effect between the metal nanoparticles and thesubstrate, completely different from the existing particle/substratesynthesis; in the aspect of applications, the present invention providesa substance comprising metal nanoparticles with enhanced Ramanspectroscopy, which makes it ideally suitable for enhancing surfaceRaman spectroscopy (SERS) effect for use in related applications,wherein the resulting nano-composite, compared to pure nanoparticles,more obviously and hugely increase the effect than that of the priorart;

4. the present invention utilizes plasma process to make large amountsof metal particles uniformly disperse in the solution or the surface ofthe substrate, proven by the analysis of effect on the present inventionwhen is applied to the surface enhanced Raman spectroscopy being beyondbetter than existing materials; and thus the present invention can beeffectively applied to the material characteristics detection,biomedical industry, food safety and environmental pollution monitoringand prevention, and other purposes; and

5. the present invention provides nanoparticles without addingadditional surfactant to achieve uniform dispersion of nanoparticles,which solves the problems in the art that requires using an organicsolvent, to rendering the process environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 being an illustrative diagram of a preferred embodiment of thereaction apparatus according to the present invention;

FIG. 2 illustrating the first preferred embodiment of the reactionapparatus of the present invention;

FIG. 3 being a schematic view of the first preferred embodiment of theinvention further provided in combination with a membrane for protonexchange;

FIG. 4 being a SEM image of the surface of the graphene substrate beforereaction;

FIG. 5 being a SEM image of the first preferred embodiment of thepresent invention, which is obtained after reaction via the methodaccording to the present invention;

FIG. 6 being a diagram obtained from a Raman signal test of the firstpreferred embodiment of the present invention;

FIG. 7 being a diagram obtained from Raman test of R6G raw material;

FIG. 8 illustrating comparison of the results between the nano-silvergraphene composite prepared by the first preferred embodiment of themethod according to the present invention the R6G only;

FIG. 9 being a SEM image of the surface of the graphene substrateobtained by the second preferred embodiment of the method according tothe present invention;

FIG. 10 illustrating comparison of the results between nano silvergraphene composite prepared by the second preferred embodiment of themethod according to the present invention and graphene only;

FIG. 11 illustrating comparison of the results between nano silvergraphene composite prepared by the second preferred embodiment of themethod according to the present invention and R6G only;

FIG. 12 being SEM image of the nano gold particle composite according tothe present invention; and

FIG. 13 being a EDS diagram of the nano gold particle compositeaccording to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the present invention provides a method forproducing a diverse multiple-dimensional nano-composite, which takesadvantage of a reaction apparatus 10, and a plasma generating device 20,wherein the reaction apparatus 10 receives a reaction liquid, thereaction liquid comprising at least one precursor of zero-dimensionalnanoparticle, where the precursor may be molecular or ionicnanoparticles. The plasma generating device 20 generates plasma onto thesurface of the reaction liquid or into the reaction liquid, and theplasma in the reaction liquid reduces or complexes the precursor to formthe zero-dimensional nanoparticles uniformly dispersed in the reactionliquid. The reaction liquid could contain a substrate, which is at leastone dimensional nanomaterial, and the substrate could be uniformlydispersed or suspended in the reaction liquid, such that thenanoparticles are reduced or generated to attach immediately to thesubstrate. The nanoparticles self-assembled to form diversemultiple-dimensional nano-composites. The at least one dimensionalnanomaterials includes nanotubes, nanowires, nanoribbon, nanosheet ornanospheres or nanopolyhedron. The at least one dimensionalnanomaterials could be a sub-micron or other magnitude. As theaforementioned process, the zero-dimensional nanoparticlesself-assembled and uniformly dispersed on the surface of the at leastone dimensional nanomaterials.

Mainly due to the use of the plasma, the reaction liquid is allowedgenerating the zero-dimensional nanoparticles, which are uniformlydispersed into the reaction liquid. The reaction liquid contents anamount of charges or charged particles or because of the molecularattraction between the particles, the zero-dimensional nanoparticleshardly aggregate and cumulate but uniformly disperse on the surface ofthe substrate.

The above plasma generating device 20 includes an atmospheric pressureplasma source or an atmospheric pressure microplasma source. The plasmacould be generated by Argon or other gases under one atmosphericpressure or a pressure close to atmospheric pressure to produce theplasma. In the present embodiment, after the plasma was generated at anatmospheric pressure and in contact with the reaction liquid,high-energy particles carried by plasma strike the surface of the liquidto form a hydrated electron. The zero-dimensional nanoparticles inreaction liquid self-assemble on the substrate by hydrated electronsreduction. The zero-dimensional nanoparticles uniformly disperse in thereaction liquid due to large amount of charge or charged particles andno aggregation occurs.

Further, the present invention has an electron receiving unit 30deposited in the reaction liquid, for receiving released electrons fromthe plasma generating device 20, and providing a continuous ion forsynthesis of metal nanoparticles. For example, when the goldnanoparticles are desired, the electron receiving unit 30 could be madeof gold to form a continuous reaction environment. The electronreceiving unit 30 provides an ionic form of desired gold nanoparticlesin the reaction liquid. The ionic form of desired gold nanoparticles arereduced to form the desired gold nanoparticles.

Further referring to Table 1, the present invention, the preferredembodiment of the reaction liquid is prepared with a precursor of thedesired metal nanoparticles, or a precursor of the desired metalnanoparticles and substrate. The precursor of the desired metalnanoparticles is preferably a salt of metal, which is dissolved in asolvent to dissociate into metal ion, such as silver ion, gold ion,copper ion and the like.

The substrate may be two-dimensional nanomaterial, three-dimensionalnanomaterial, which include but not limited to graphene, functionalizedgraphene, molybdenum disulfide (MoS₂), graphene nanoribbon (GNR) orcarbon nanotube (CNT) uniformly distributed in the reaction liquid. Thegenerated nanoparticles are adsorbed or adhered to at least a portion ofthe surface of the substrate.

TABLE 1 Metal for silver (Ag), gold (Au), copper (Cu), platinum (Pt),synthesized of iridium (Ir), ferrum (Fe) Precursor silver nitrate,Chloroauric Acid, Copper(II) Sulfate, thereof Dihydrogenhexachloroplatinate (IV) hexahydrate, Iridium(III) chloride trihydrate,iron(III) oxide Substrate graphene, MoS₂, graphene nanoribbon (GNT),carbon thereof nano tube (CNT)

The reaction liquid may further add polysaccharides or other polymers toprevent the nanoparticles agglomeration. The polysaccharides may be butnot limited to fructose or glucose. The said polymers may be, forexample, polyvinylpyrrolidone (PVP) or trisodium citrate (TSC). Thepolyvinylpyrrolidone (PVP) and the trisodium citrate have a slightreduction effect, thus to enhance reduction of the nanoparticles.

When depositing the electron receiving unit 30, the substrate could beonly uniformly dispersed in the reaction liquid, the precursor may notbe necessary during using the electron receiving unit 30. Only when theplasma is applied to the reaction liquid, the electron receiving unit 30continues to provide an ion for synthesis of nanoparticles in thereaction liquid. Desired nanoparticles are synthesized by reduction, andmeanwhile they self-assemble on and attach to the local surface of thesubstrate.

Referring to FIG. 2, the plasma generating device 20 could produceplasma through the use of high-voltage high-power resistor or voltagestabilizing circuit to stably introduce the current (high voltage andlow current (mA)), and then introduce the plasma gas argon (Ar) or otherreaction gas to form normal pressure plasma or microplasma.

EXAMPLE 1

The first preferred embodiment of the present invention is manufactureof silver nanoparticles. The reaction apparatus 10 contained a reactionliquid containing a solution of silver nitrate at a concentrationranging from about 1 mM to 0.01 M, graphene and fructose.

The plasma generating device 20 applied a plasma to the reaction liquid.The plasma with high-energy particles struck the surface of the reactionliquid and produced hydrated electrons to obtain silver nanoparticles byreduction. The equation of the reaction in the reaction liquid was asfollowed:

e_(aq)+Ag⁺→Ag

e_(aq)H→H₂+OH⁻

Ag⁺+e_(aq)→Ag⁰→small Ag cluster→Ag nano particles

Referring to FIG. 3, the present invention could be further providedwith a proton exchange membrane in the reaction liquid to achieve thesame reaction process.

Referring to Table 2, using the method of Example 1, the presentinvention is applicable to the manufacture of other metal nanoparticles,wherein the ratio of the concentration of the reaction liquid to theadded material was shown in Table 2.

TABLE 2 Zero- dimensional Concentration of the metal precursor of thedesired nanoparticle metal nanoparticles substrate electrolyte silverSilver nitrate for about1 graphene fructose, mM~0.01M nitric acid goldChloroauric acid for about graphene fructose, 1 mM~0.01M hydrochloricacid copper copper sulfate for about1 graphene fructose, mM~0.01M nitricacid platinum chloroplatinic acid for graphene sodium chloride, 1mM~0.01M hydrochloric acid iron ferric oxide for about graphene sodiumchloride 5~10 wt % iridium iridium trichloride for graphene citric acidabout 1 mM~0.01M

EXAMPLE 2

Illustrated was the second preferred embodiment of the presentinvention, wherein the electron receiving unit 30 could be an electrodefor directly providing zero-dimensional nanoparticles, such as a silverelectrode, a gold electrode, a copper electrode or a carbon rod. Whenthe plasma generating device 10 provided a large amount of high-energyelectrons in the reaction liquid, the electron receiving unit 30released ions of the zero-dimensional nanoparticles to react with theelectrons to generate the zero-dimensional nanoparticles by reduction.The system according to the present embodiment was applicable tomanufacture of various metal nanoparticles and further attached to aportion or entire surface of the substrate to generate a diversemultiple-dimensional nanocomposite.

As described in Example 1, the present embodiment was further providedwith a proton-exchange membrane in the reaction liquid.

Referring to Table 3, the suitable materials added in the reactionliquid of Example 2 were listed.

TABLE 3 Type of electron receiving unit Type of substrate Type ofelectrolyte silver electrode graphene fructose, nitric acid goldelectrode graphene fructose, hydrochloric acid copper electrode graphenefructose, nitric acid

Referring to FIG. 4 and FIG. 5, FIG. 4 demonstrated a SEM image of thesurface of graphene substrate before reaction. FIG. 5 demonstrated a SEMimage of the surface of graphene substrate according to the reactionmethod according the first preferred embodiment of the presentinvention, wherein the surface of the substrate was attached with manysilver nanoparticles, demonstrating the metal nanoparticles could besuccessfully attached to the surface of graphene substrate.

Referring to FIGS. 12 to 13, an electronic microscopy and EDS detectionresult shown the growing gold nanoparticles on the surface of thesubstrate. As shown in FIG. 12, after the plasma treatment, the surfaceof the substrate formed nanoparticles. With further elemental analysisby EDS, the formed nanoparticles on the surface of the substrate weremade of gold. According to this result, the method according to thepresent invention is useful for effectively forming nanoparticles onvarious substrates and nanoparticles are self-assembled on thesubstrate, generating the diverse multiple-dimensional nano-composite.

As the aforementioned Examples, the method according to the presentinvention can be very efficient to allow nanoparticles self-assemblingon selected substrates. The resultant diverse multiple-dimensionalnano-composite may have two different characteristics, diversemultiple-dimensional nanomaterials, and can generate novel and uniquematerial properties. It was proven that, to form different combinationsof a metal or non-metallic materials of zero-dimensional nanomaterialsand a substrate, the reaction liquid, the precursor and the substrateare selected to achieve the desired effect that cannot be reached by theprior art.

The metal and metal nano-composite could be a material for enhancingenhance factor while measured by Raman spectrum of the surface of thematerial. In general, the spontaneity of the Raman scattering is veryweak, such that Raman spectroscopy measurement results are usuallydifficult to identify, leading to difficulties in measurement. Theobtained nano-composite according to the present invention uniformlydisperse on a substrate surface, such that when used with other materialfor analysis, the testing incident light can enhance Raman spectroscopyof the analyte signal by metal nanoparticles/substrate to more clearlyidentify the test substance.

Referring to FIG. 6, A which represented the nano-composite obtainedfrom silver ions and graphene according to the first embodiment of thepresent invention, was enhanced by 70 times in Comparison to B, Ramansignal of the pure graphene. Therefore, in terms of application ofsurface enhanced Raman spectroscopy (SERS), the present inventionacquired a better surface enhanced Raman spectroscopy effect incomparison to the current technique being directly mixing metalparticles with graphene without complete association therebetween.

Referring to FIGS. 7 to 8, FIG. 7 demonstrated a signal of Rhodamine 6G(R6G) in Raman signal test, showing intensity of the R6G feature peaksto be only around dozens. Comparing the silver and graphenenano-composite according to the first preferred embodiment of thepresent invention in FIG. 8 and Raman signal of R6G in FIG. 7, thatpanel (a) represented silver and graphene nano-composite prepared byExample 1 of the present invention by using a current of 4 mA, areaction time of 20 minutes, panel (b) represented silver and graphenenano-composite prepared by Example 1 of the present invention by using acurrent of 5 mA, a reaction time of 20 minutes, panel (c) representedsilver and graphene nano-composite prepared by Example 1 of the presentinvention by using a current of 6 mA, a reaction time of 20 minutes, andpanel (d) represented silver and graphene nano-composite prepared byExample 1 of the present invention by using a current of 7 mA, areaction time of 20 minutes. Comparing to the R6G test results, Ramansignal of the nanoparticles obtained by Example 1 of the presentinvention was enhanced to about 10 to 60 times.

Referring to FIGS. 4 and 9, FIG. 4 was a SEM image of the surface of thegraphene substrate before reaction, and the FIG. 9 was a SEM image ofthe surface of the graphene prepared by the second preferred embodimentof the method according to the present invention, wherein silvernanoparticles were attached to the graphene substrate, showing thesuccess of the present invention to form metal nanoparticles on thesurface of the graphene substrate.

Referring to FIGS. 7, 10 to 11, C in FIG. 10 showed a Raman signaldiagram of the silver and graphene nano-composite prepared by Example 2of the present invention. Comparing to D, a test result of pure graphenematerial, the present invention could increase the Raman signal to about200 times. Comparing Raman signal test result of pure R6G in FIG. 7,silver and graphene nano-composite prepared by Example 2 of the presentinvention as shown in FIG. 11, the present invention further increasedRaman signal to about 100 to 400 times.

According to the above results, by using reaction system as the secondpreferred embodiment of the present invention, the surface of thesubstrate was able to absorb more of the metal nanoparticles, leading toa resultant enhanced Raman scattering spectra effect higher than that ofthe first preferred embodiment of the invention. The main factor couldbe that direct use of electrode made of an element of the syntheticnanoparticles in the second preferred embodiment, comparing to the firstpreferred embodiment of the present invention. Therefore, in the secondpreferred embodiment of the present invention, the substrate can adsorbmore nanoparticles on its surface. According to the above description,the present invention has the following advantages:

1. the present invention provides a method for directly producing alarge amount of nanoparticles with evenly dispersion through theadjustment of formulation to generate nanoparticles directly synthesizedor attached on a surface of a selected substrate, nanoparticles beinguniformly attached to the surface of the substrate, which results in anadvanced method of producing a self-assembled nano-composite havingmultiple-dimensional structure to solve the problem in industrialproduction of nanoparticles, and more to solve the problem in redundantprocedure for dispersion of nanoparticles or nano-composites;

2. the present invention provides a solution for resolving the need ofnanomaterials for different purpose, by choosing desired nanoparticlesand substrates to obtain various diverse multiple-dimensionalnano-composite, which result from precise choice of material to grow toconcur the barrier of current technique to provide a more diverse, lessrestrictive, more simple and efficient method for producing the same;

3. the present invention utilizes plasma manufacturing process toincrease absorption effect between the metal nanoparticles and thesubstrate, completely different from the existing particle/substratesynthesis; in the aspect of applications, the present invention providesa substance comprising metal nanoparticles with enhanced Ramanspectroscopy, which makes it ideally suitable for enhancing surfaceRaman spectroscopy (SERS) effect for use in related applications,wherein the resulting nano-composite, compared to pure nanoparticles,more obviously and hugely increase the effect than that of the priorart;

4. the present invention utilizes plasma process to make large amountsof metal particles uniformly disperse in the solution or the surface ofthe substrate, proven by the analysis of effect on the present inventionwhen is applied to the surface enhanced Raman spectroscopy being beyondbetter than existing materials; and thus the present invention can beeffectively applied to the material characteristics detection,biomedical industry, food safety and environmental pollution monitoringand prevention, and other purposes; and

5. the present invention provides nanoparticles without addingadditional surfactant to achieve uniform dispersion of nanoparticles,which solves the problems in the art that requires using an organicsolvent, to rendering the process environmentally friendly.

What is claimed is:
 1. A method for producing nano-composite, comprisingthe steps of: providing a reaction solution containing at least onedimensional nanomaterials and a precursor of zero-dimensionalnanoparticles; and applying plasma to a surface of the reaction solutionor in the reaction solution to generate the zero-dimensionalnanoparticles from the precursor to assemble on the at least onedimensional nanomaterials to obtain the nano-composite; whereby thenanoparticles self-assemble on the surface of the at least onedimensional nanomaterials in the reaction solution to form thenano-composite dispersed in the reaction solution.
 2. The methodaccording to claim 1, wherein the zero-dimensional nanoparticles includemetal or non-metal nanoparticles; and the at least one dimensionalnanomaterials contain nanotubes, nanowires, nanoribbon, nano-plateletsor nano-spheres.
 3. The method according to claims 1, wherein the plasmais atmospheric plasma or microplasma; the zero-dimensional nanoparticlesare silver nanoparticles, gold nanoparticles, copper nanoparticles,platinum nanoparticles, iridium nanoparticles or iron nanoparticles; andthe at least one dimensional nanomaterials comprise nanoparticles ofgraphene, functionalized graphene or molybdenum disulfide, graphenenanoribbon, or carbon nanotubes.
 4. The method according to claims 2,wherein the plasma is atmospheric plasma or microplasma; thezero-dimensional nanoparticles are silver nanoparticles, goldnanoparticles, copper nanoparticles, platinum nanoparticles, iridiumnanoparticles or iron nanoparticles; and the at least one dimensionalnanomaterials are nanoparticles of graphene, functionalized graphene ormolybdenum disulfide, graphene nanoribbon, or carbon nanotubes.
 5. Themethod according to claim 3, wherein the reaction solution furthercontains silver nitrate, chloroauric acid, copper sulfate,chloroplatinic acid, iridium trichloride or ferric oxide.
 6. The methodaccording to claim 4, wherein the reaction solution further containssilver nitrate, chloroauric acid, copper sulfate, chloroplatinic acid,iridium trichloride or ferric oxide.
 7. A diverse multiple-dimensionalnano-composite, which is formed by binding zero-dimensionalnanoparticles to surfaces of at least one dimensional nanomaterials,wherein the zero-dimensional nanoparticles bind to the surfaces of theat least one dimensional nanomaterials by the electrical potentialdifference, surface characteristics or attraction between molecules. 8.The diverse multiple-dimensional nano-composite according to claim 7,wherein the zero-dimensional nanoparticles include metal or non-metalnanoparticles; the at least one dimensional nanomaterials containnanotubes, nanowires, nanoribbons, nano-platelets or nano-spheres. 9.The diverse multiple-dimensional nano-composite according to claims 7,wherein the zero-dimensional nanoparticles are silver nanoparticles,gold nanoparticles, copper nanoparticles, platinum nanoparticles,iridium nanoparticles or iron nanoparticles; and the at least onedimensional nanomaterials are nanoparticles of graphene, functionalizedgraphene or molybdenum disulfide, carbon nanotubes or graphenenanoribbons.
 10. The diverse multiple-dimensional nano-compositeaccording to claims 8, wherein the zero-dimensional nanoparticles aresilver nanoparticles, gold nanoparticles, copper nanoparticles, platinumnanoparticles, iridium nanoparticles or iron nanoparticles; and the atleast one dimensional nanomaterials are nanoparticles of graphene,functionalized graphene or molybdenum disulfide, carbon nanotubes orgraphene nanoribbons.
 11. The diverse multiple-dimensionalnano-composite according to claim 7, wherein the zero-dimensionalnanoparticles and the at least one dimensional nanomaterials aresubjected to a more than one-atmospheric pressure or a low pressureplasma to have electric potential difference, different charge, surfacecharacteristics or attraction between molecules.